The present invention is directed to the field of ophthalmic surgery. More specifically, the invention is directed to the field of procedures and associated products for removing the natural crystalline lens of the human eye in patients whose lenses have become afflicted with cataracts or other conditions wherein removal of the lenses is required.
Removal of human lenses has been achieved by various surgical techniques in the past. The most prevalent technique at this time involves a process known as “phacoemulsification”. This process involves the use of a handpiece with a tip that vibrates at an ultrasonic frequency. After making a small incision in the eye, the ophthalmic surgeon employs this handpiece to emulsify the lens within the capsular bag of the eye, and then employs the irrigation and aspiration modes of the handpiece to remove the lens particles from the capsular bag. Millions of cataract patients have had their cataractous lenses removed by means of the phacoemulsification procedure. Although ophthalmic surgeons have mastered the use of the phacoemulsification handpiece and associated surgical techniques, the use of an ultrasonic needle or tip within the eye presents inherent risks and concerns. Ophthalmic surgeons and others skilled in the art have therefore searched for improved devices and procedures for removing the human lens.
A new lens removal procedure known as “liquefracture” is currently being developed by Alcon Research, Ltd. This procedure is described in U.S. Pat. No. 5,616,120 (Andrew, et al.), U.S. Pat. No. 5,885,243 (Capetan, et al.), U.S. Pat. No. 5,989,212 (Sussman, et al.), U.S. Pat. No. 5,997,499 (Sussman, et al.) and U.S. Pat. No. 6,080,128 (Sussman, et al.), the entire contents of the foregoing patents are hereby incorporated in the present specification by reference.
Liquefracture is a new technique wherein the lens is disintegrated by applying hot pulses of a solution to the lens via an irrigation/aspiration handpiece. The handpiece, such as those described in the above-cited patents, includes a chamber for heating the solution and generating pulses of heated solution that are expelled from the handpiece. The lens is disintegrated by means of a combination of the heat absorbed from the solution and the force of the pulses of the solution impacting the lens tissue. The solution utilized for this purpose is referred to herein as the “liquefracture solution”.
Due to the delicacy of the intraocular tissues, both the extent to which the solution can be heated and the force or velocity of the pulses are necessarily constrained. In order to prevent damage to surrounding tissues, the stream of hot, pulsed solution is surrounded by a conventional irrigating solution which dissipates both the heat and force of the pulsed solution after it impacts the lens tissue. This second solution is referred to herein as either the “irrigating solution” or the “outer” or “dissipating” solution.
Prior to the present invention, the solution utilized for both the liquefracture solution and the irrigating solution has been a conventional balanced salt solution such as BSS® (Balanced Salt Solution) Sterile Irrigating Solution, which is available from Alcon Laboratories, Inc., Fort Worth, Tex. Although this type of solution is generally adequate, there is a need for improved solutions which enhance the disintegration of the lens with the pulsed, heated solution and facilitate removal of the lens fragments following disintegration of the lens. The present invention is directed to filling this need.